1. Field of the Invention
The present invention relates to a thin film magnetic head which is used for the recording/reproducing on a magnetic recording medium, a method for manufacturing the thin film magnetic head, and a magnetic storage apparatus including the thin film magnetic head.
2. Description of the Related Art
With the increase of the recording density of magnetic storage apparatuses, coercivity required of recording media is also advancing higher and higher, and as magnetic core material for recording heads, materials having high saturation magnetic flux density (Bs), that is, materials capable of outputting a strong magnetic field sufficient for the writing to the high-coercivity medium, are being required. Such materials having high saturation magnetic flux density (Bs) include CoNiFe (Bs: 1.7 T) whose Bs is higher than that of Ni45Fe55 (Bs: 1.6 T) which is being generally used as magnetic core material, as described in JP-A-6-89422, JP-A-8-241503, JP-A-6-346202 and JP-A-7-3489. JP2821456 also discloses a method for forming a plating layer having still higher Bs using a plating bath that does not contain saccharin sodium as a component of the plating solution.
In order to realize a high-recording-density magnetic storage apparatus, the use of such material having high saturation magnetic flux density (Bs) and being capable of outputting a strong magnetic field sufficient for the writing to a high-coercivity medium and a technique for forming a stable and thick magnetic core for the generation of a stronger magnetic field are both essential.
However, such a technique for the formation of a stable and thick magnetic core has not been established yet at present, and thus there has been realized no thin film magnetic head that is capable of generating a strong magnetic field sufficient for the writing to the high-coercivity medium.
It is therefore the primary object of the present invention to provide a thin film magnetic head that is capable of generating a strong magnetic field sufficient for the writing to a high-coercivity medium (of coercivity of 4000 Oe, for example), a method for manufacturing such a thin film magnetic head, and a magnetic storage apparatus including such a thin film magnetic head.
In order to form a magnetic layer (as the magnetic core) with high precision and to a considerable thickness, it is effective to employ electroplating. For carrying out the electroplating, an xe2x80x9cunderlayerxe2x80x9d, that is, a thin electrical conducting layer which is formed by sputtering, CVD (Chemical Vapor Deposition), etc., becomes necessary.
Therefore, the present inventors conducted close examination of the underlayers and found out that the formation of a magnetic core capable of outputting a strong magnetic field sufficient for the writing to high-coercivity media becomes possible by controlling the saturation magnetic flux density of the underlayer and that of the magnetic layer which is formed on the underlayer.
The thin film magnetic head, the method for manufacturing the thin film magnetic head, and the magnetic storage apparatus including the thin film magnetic head in accordance with the present invention were completed on the basis of the above finding. In a magnetic head comprising a lower magnetic pole, an upper magnetic pole which is provided so as to face the lower magnetic pole, and a magnetic gap layer which is provided between the lower magnetic pole and the upper magnetic pole, the upper magnetic pole includes a first magnetic layer which is formed on a side facing the magnetic gap layer by means of sputtering and a second magnetic layer which is formed on the first magnetic layer by means of plating. The saturation magnetic flux density of the first magnetic layer is set higher than that of the second magnetic layer.
The thin film magnetic head in accordance with the present invention having the above composition is capable of generating a stronger magnetic field owing to its stably-formed magnetic core.